Each year 200,000 women in the US are diagnosed with breast cancer, and 40,000 women will die of the disease. Serum diagnosis for screening breast cancer patients is not yet available. Moreover, there is only limited possibility for monitoring response to therapy of breast cancer patients. A serum bioassay that works hand-in-hand with therapy for the diagnosis and/or the monitoring of breast cancer patients is desperately needed. We have identified PC-Cell Derived Growth Factor (PCDGF/GP88) as a molecular target for the development of breast cancer therapy and diagnosis. Biological and pathological studies have demonstrated the critical role of PCDGF in breast carcinoma. PCDGF is overexpressed in human breast carcinoma. Inhibition of PCDGF expression leads to the inhibition of tumor growth in nude mice. PCDGF is overexpressed in 80% of invasive ductal carcinoma in correlation with clinical parameters of poor prognosis whereas normal tissues and benign lesions are negative. Therapy development based on inhibiting PCDGF action on breast cancer cells is currently being developed at A&G Pharmaceutical. Recently, A&G Pharmaceutical has developed an EIA to detect circulating PCDGF level in serum and plasma. We have established a baseline for PCDGF serum level in control individuals, and showed with a limited number of patients that PCDGF level was elevated in patients with progressive disease. This SBIR Phase I focuses on a large-scale feasibility study to determine the potential of serum PCDGF assay for the diagnosis of breast cancer patients. Methods: Circulating PCDGF will be measured by EIA using serum samples from 600 breast cancer patients collected at 4 specific time points: before surgery, after surgery, after 6 months and one year of therapy. 110 matched control serum samples will also be analyzed. Data will be statistically analyzed and correlated to clinical parameters and response to therapy. This SBIR Phase I study will lay the foundation for Phase II application by establishing proof of concept. By the end of Phase II program, A&G expects to complete all diagnostic clinical trials necessary for FDA 510K application for the serum PCDGF determination kit to be used for diagnosis and/or monitoring of breast cancer patients.